Control of the air-fuel (A/F) ratio (λ) of the exhaust gas entering an automotive catalyst, such as a three-way catalyst (TWC), may be necessary for optimal conversion of unwanted tailpipe emissions. The conversion of emissions such as nitrogen oxides (NOx), hydrocarbons (HC), and CO may all be affected by the A/F ratio. If the A/F ratio is not controlled properly, unwanted emissions may escape from a vehicle. In order to accurately control the A/F ratio, sensors or other detection devices may be placed up and/or downstream of the catalyst. However, this equipment may not always be accurate/calibrated and may experience changes over time or from environmental conditions.